阅读说明：本技术 一种25.4mm热连轧极限规格管线钢板卷及其制造方法 (25.4mm hot continuous rolling limit specification pipeline steel plate coil and manufacturing method thereof ) 是由 邹航 李利巍 徐进桥 岳江波 徐锋 梅荣利 李鹏程 于 2021-06-29 设计创作，主要内容包括：本发明涉及热轧管线钢领域,公开了一种25.4mm热连轧极限规格管线钢板卷,其化学成分的质量百分比为：C：0.029～0.051％,Si：0.13～0.27％,Mn：1.08～1.63％,P：≤0.012％,S：≤0.0015％,Mo：0.07～0.15％,Nb：0.037～0.059％,Ti：0.013～0.024％,Al：0.011～0.037％,Mg：0.0003～0.0011％,O：0～0.0015％,N：≤0.0045％,其余为Fe及不可避免杂质。本发明还公开了一种25.4mm热连轧极限规格管线钢板卷的制造方法。本发明25.4mm热连轧极限规格管线钢板卷及其制造方法,获得了组织超细化和均匀化的25.4mm热连轧极限规格管线钢板卷,并具备良好的低温韧性。(The invention relates to the field of hot-rolled pipeline steel, and discloses a 25.4mm hot continuous rolling limit specification pipeline steel plate coil, which comprises the following chemical components in percentage by mass: c: 0.029-0.051%, and Si: 0.13 to 0.27%, Mn: 1.08-1.63%, P: less than or equal to 0.012 percent, S: less than or equal to 0.0015 percent, Mo: 0.07 to 0.15%, Nb: 0.037-0.059%, Ti: 0.013-0.024%, Al: 0.011-0.037%, Mg: 0.0003-0.0011%, O: 0-0.0015%, N: less than or equal to 0.0045 percent, and the balance of Fe and inevitable impurities. The invention also discloses a manufacturing method of the 25.4mm hot continuous rolling limit specification pipeline steel plate coil. The 25.4mm hot continuous rolling limit specification pipeline steel plate coil and the manufacturing method thereof obtain the 25.4mm hot continuous rolling limit specification pipeline steel plate coil with ultra-fine and uniform structure and good low-temperature toughness.)

1. The utility model provides a 25.4mm hot continuous rolling limit specification pipeline steel sheet book which characterized in that: the weight percentage of the chemical components is as follows: c: 0.029-0.051%, and Si: 0.13 to 0.27%, Mn: 1.08-1.63%, P: less than or equal to 0.012 percent, S: less than or equal to 0.0015 percent, Mo: 0.07 to 0.15%, Nb: 0.037-0.059%, Ti: 0.013-0.024%, Al: 0.011-0.037%, Mg: 0.0003-0.0011%, O: 0-0.0015%, N: less than or equal to 0.0045 percent, and the balance of Fe and inevitable impurities.

2. The 25.4mm hot continuous rolling limit specification pipeline steel plate coil of claim 1, wherein: the chemical components also comprise: at least one of Cu, Ni, Cr, B, V and Ca, wherein the mass percentage of Cu: less than or equal to 0.30 percent, Ni: less than or equal to 0.30 percent, Cr: less than or equal to 0.30 percent, B: less than or equal to 0.0005%, V: less than or equal to 0.030 percent, Ca: less than or equal to 0.0020 percent.

3. The 25.4mm hot continuous rolling limit specification pipeline steel plate coil of claim 1, wherein: when the C content is 0.029 to 0.045%, the Mn content is 1.42 to 1.63%.

4. The 25.4mm hot continuous rolling limit specification pipeline steel plate coil of claim 1, wherein: when the C content is 0.046-0.051%, the Mn content is 1.08-1.41%.

5. The 25.4mm hot continuous rolling limit specification pipeline steel plate coil of claim 1, wherein: p: less than or equal to 0.010 percent, S: less than or equal to 0.0010 percent, N: less than or equal to 0.0040 percent.

6. The 25.4mm hot continuous rolling limit specification pipeline steel plate coil of claim 1, wherein: the structure is characterized in that the acicular ferrite and the refined granular bainite or quasi-multi-deformation ferrite are adopted, the proportion of the acicular ferrite at the 1/4-position of the plate thickness is not less than 75 percent, the proportion of the refined granular bainite or quasi-multi-deformation ferrite is not more than 25 percent, and the size is not more than 6 mu m; the proportion of acicular ferrite at 1/2 position of the plate thickness is not less than 50%, the proportion of refined granular bainite or quasi-multi-deformed ferrite is not more than 50%, and the size is not more than 8 μm.

7. A method for manufacturing 25.4mm hot continuous rolling limit specification pipeline steel plate coils according to any one of claims 1 to 7, which is characterized by comprising the following steps: the method comprises the following steps:

A) smelting and casting: smelting, refining and continuously casting according to components to obtain a plate blank, wherein the thickness of the plate blank is 230 mm;

B) cooling the plate blank: cooling the slab to below 420 ℃;

C) heating the plate blank: heating the cooled plate blank, wherein the temperature of heating furnace gas in the heating process is not more than 1200 ℃ in the whole process, the discharging temperature of the plate blank is 1130-1170 ℃, and the temperature is kept above 1130 ℃ for 90-120 min;

D) rough rolling: rolling the plate blank discharged from the furnace in the step C), wherein the rolling pass is 5-6 passes, the final rolling temperature of rough rolling is 930-990 ℃, the thickness of the plate blank after the rough rolling is 58-62 mm, when each pass of rough rolling enters the rolling mill, starting high-pressure water for descaling, and the rolling speed of the last two passes is 3-4 m/s;

E) finish rolling: finish rolling the plate blank after the rough rolling in the step D) by a 7-stand continuous rolling unit, wherein the finish rolling is performed for 5-6 times, the initial rolling temperature is lower than 930 ℃, and the final rolling temperature is 780-820 ℃;

F) and (3) controlling cooling: cooling to 250-370 ℃ at a speed of 25-45 ℃/s, and coiling.

8. The method for manufacturing 25.4mm hot continuous rolling limit specification pipeline steel plate coil according to claim 4, wherein the method comprises the following steps: in said step a), the Mg treatment follows the RH vacuum treatment and is added as an Al — Mg alloy wire.

9. The method for manufacturing 25.4mm hot continuous rolling limit specification pipeline steel plate coil according to claim 4, wherein the method comprises the following steps: in the step D), the pass reduction rate of the last two passes of rough rolling is not lower than 23%.

10. The method for manufacturing 25.4mm hot continuous rolling limit specification pipeline steel plate coil according to claim 4, wherein the method comprises the following steps: in the step E), the 4 th to 5 th frames or the 4 th frame is nominal.

Technical Field

The invention relates to the field of hot-rolled pipeline steel, in particular to a 25.4mm hot continuous rolling limit specification pipeline steel plate coil and a manufacturing method thereof.

Background

In order to improve the conveying capacity of oil and gas pipelines, pipeline design is increasingly developed towards high pressure and large caliber, so that the pipeline material is required to have higher steel grade and larger thickness specification, and good low-temperature toughness is ensured.

In the prior art, the maximum plate blank thickness of a conventional hot continuous rolling production line is 230mm generally, and when a thick plate coil is rolled, the integral compression ratio is low, so that the deformation recrystallization refining effect is not obvious; and the deformation and the uneven structure in the thickness direction, especially the coarsening of the crystal grains at the center of the plate thickness is remarkable.

Therefore, the above problems lead to an increase in difficulty in controlling low-temperature toughness of a thick-gauge pipeline steel coil, and the greater the thickness of the coil, the greater the difficulty in controlling low-temperature toughness. And the 25.4mm hot continuous rolling limit specification pipeline steel is the extreme result of the pipeline steel plate coil product.

Chinese patents (published: 2015: 07 and 22 days, publication number: CN104789887A) disclose an ultra-thick specification HIC-resistant and SSCCX-resistant 65 pipeline steel plate and a manufacturing method thereof, Chinese patents (published: 2016: 06 and 15 days, publication number: CN105665443A) disclose a rolling process for producing extreme specification pipeline steel by a wide and thick plate rolling mill, and Chinese patents (published: 2019, 09 and 06 days, publication number: CN110205553A) disclose a production method for thick specification X70 grade pipeline steel with excellent low-temperature DWTT performance, wherein the patents relate to components and a production process for producing thick specification pipeline steel plates by a wide and thick plate production line. However, due to the difference in equipment between the wide and thick plate production line and the hot continuous rolling production line, the components, the process and the final structure design of the wide and thick plate production line are different, so that the components and the process design of the wide and thick plate production line are not suitable for the production of thick pipeline steel plate coils by the hot continuous rolling production line.

Chinese patent (published: 2020, 11.02/11.CN 110777296A) discloses an ultra-thick X52 pipeline steel hot-rolled coil and a production method thereof, wherein the thickness specification reaches 24mm, and the requirements of X52-grade pipeline steel on the performance can be met by stretching, impact and the like, but the qualified DWTT performance cannot be ensured by the design of components (relatively high C content and the like) and processes (high-temperature coiling, low-speed cooling and the like).

Chinese patent (published: 2016, 26 months and 26 days, publication number: CN106048181A) discloses a preparation method of low-temperature thick-specification pipeline steel suitable for a hot continuous rolling production line, and the process method is suitable for batch production of 12-18 mm-thickness specification pipeline steel plate coils, but has insufficient DWTT performance when producing limit specification pipeline steel plate coils.

Disclosure of Invention

The invention aims to overcome the defects of the technology and provide a 25.4mm hot continuous rolling limit specification pipeline steel plate coil and a manufacturing method thereof, wherein the 25.4mm hot continuous rolling limit specification pipeline steel plate coil with ultra-fine and uniform structure is obtained, and the coil has good low-temperature toughness.

In order to achieve the aim, the 25.4mm hot continuous rolling limit specification pipeline steel plate coil designed by the invention comprises the following chemical components in percentage by mass: c: 0.029-0.051%, and Si: 0.13 to 0.27%, Mn: 1.08-1.63%, P: less than or equal to 0.012 percent, S: less than or equal to 0.0015 percent, Mo: 0.07 to 0.15%, Nb: 0.037-0.059%, Ti: 0.013-0.024%, Al: 0.011-0.037%, Mg: 0.0003-0.0011%, O: 0-0.0015%, N: less than or equal to 0.0045 percent, and the balance of Fe and inevitable impurities.

Preferably, the chemical composition further comprises: at least one of Cu, Ni, Cr, B, V and Ca, wherein the mass percentage of Cu: less than or equal to 0.30 percent, Ni: less than or equal to 0.30 percent, Cr: less than or equal to 0.30 percent, B: less than or equal to 0.0005%, V: less than or equal to 0.030 percent, Ca: less than or equal to 0.0020 percent.

Preferably, when the C content is 0.029 to 0.045%, the Mn content is 1.42 to 1.63%.

Preferably, when the C content is 0.046-0.051%, the Mn content is 1.08-1.41%.

Preferably, P: less than or equal to 0.010 percent, S: less than or equal to 0.0010 percent, N: less than or equal to 0.0040 percent.

Preferably, the structure is characterized by acicular ferrite and refined granular bainite or quasi-multi-deformation ferrite, the proportion of the acicular ferrite at the position of 1/4 mm of the plate is not less than 75%, the proportion of the refined granular bainite or quasi-multi-deformation ferrite is not more than 25%, and the size is not more than 6 μm; the proportion of acicular ferrite at 1/2 position of the plate thickness is not less than 50%, the proportion of refined granular bainite or quasi-multi-deformed ferrite is not more than 50%, and the size is not more than 8 μm.

In the chemical composition design of the invention:

carbon (C): the most economical strengthening elements improve the strength of the steel through interstitial solid solution strengthening, and simultaneously greatly improve the hardenability of the steel, thereby being beneficial to low-temperature phase change. For the extreme specification pipeline steel plate coil, in order to obtain ideal structure performance, high cooling speed cooling is needed, when the C content is too high, the structure performance of the material in the plate thickness direction is seriously uneven, the cold bending cracking tendency is increased, and the DWTT performance is not good; c too low decreases the strength of the steel. The proper addition amount of C is 0.029-0.051%.

Silicon (Si): mainly plays a role in solid solution strengthening and is beneficial to the desulfurization in the auxiliary smelting process. The appropriate amount of Si added is 0.13-0.27%.

Manganese (Mn): the hardenability of the steel can be improved, and the yield strength and the tensile strength of the steel are obviously improved. However, Mn belongs to easily segregated elements, so that the austenite stability of a segregation part is increased, the diffusion of C to the segregation part is further accelerated in the phase transformation process, and a brittle and hard martensite phase is finally formed, which is unfavorable for the toughness of the material; particularly, severe segregation at the center of the sheet thickness is often a cause of fracture separation, and the appropriate amount of Mn is 1.08 to 1.63%.

Phosphorus, sulfur, nitrogen (P, S, N): p, S, N it is a harmful element in the pipeline steel, and its content should be controlled as much as possible.

Molybdenum (Mo): the element with strong hardenability obviously improves the stability of austenite, delays the phase change of high-temperature ferrite and is beneficial to the formation of acicular ferrite; and Mo has low segregation degree in steel, and the nonuniformity of the material structure performance can not be aggravated under the condition of proper alloy and process design. However, for the pipeline steel plate coil with the limit specification, the proper Mo addition can obviously improve the structural uniformity in the plate thickness direction and improve the low-temperature toughness of the steel plate; however, when the content of Mo is too high, the size and proportion of martensite islands are too high, and the DWTT performance of the plate coil is not facilitated. The appropriate addition amount of Mo is 0.07-0.15%.

Niobium, titanium (Nb, Ti): the microalloying elements can obviously refine grains and play a role in precipitation strengthening, and meanwhile, the austenite recrystallization temperature of the steel can be obviously improved, the range of a non-recrystallization region is expanded, the increase of accumulated strain in the non-recrystallization region is facilitated, and the phase change of acicular ferrite in the cooling control process is promoted. The appropriate addition amounts of Nb and Ti are 0.037-0.059% and 0.013-0.024%, respectively.

Aluminum, magnesium (Al, Mg): the Al-Mg-Al spinel alloy is deoxidizing elements in steel, and is added compositely with Al and Mg to form dispersed magnesium-Al spinel composite inclusions (large-size inclusions are reduced remarkably, and inclusions below 2 mu m are increased greatly), so that the Al-Mg-Al spinel alloy plays a role in refining grains in the continuous casting process, becomes particles for promoting acicular ferrite nucleation, and is beneficial to improving the welding performance. The proper addition amounts of Al and Mg are 0.011-0.037% and 0.0003-0.0011%, respectively.

Oxygen (O): residual elements are inevitable in the smelting process of steel. Combined with Al, Mg, form dispersed oxide inclusions in the steel. However, the O content is strictly limited, and when the O content is too high, the size and the number of inclusions are both greatly increased, which is unfavorable for the low-temperature toughness of the steel. The content of O is properly controlled within 0.0015 percent.

Copper, nickel (Cu, Ni): cu has a certain solid solution strengthening effect and improves the corrosion resistance of steel, but Cu is not suitable to be added independently; ni can improve the low-temperature toughness of the material and can improve the surface brittleness caused by Cu. The proper addition amount of Cu and Ni is less than or equal to 0.30 percent.

Chromium (Cr): improving the hardenability of the steel and the solid solution strengthening effect. However, when the Cr content is too high, the welding performance is not good; and the segregation degree is close to Mn, which is not favorable for controlling the uniformity of the material structure. The proper addition amount of Cr is less than or equal to 0.30 percent.

Vanadium (V): the microalloying elements are difficult to precipitate under the production process conditions of pipeline steel, mainly play a role in solid solution strengthening, and particularly can obviously improve the tensile strength and reduce the yield ratio, but the impact toughness of the steel can be reduced when the content of vanadium is too high. The proper addition amount of V is less than or equal to 0.030 percent.

Calcium (Ca): calcium treatment is carried out on the steel in the secondary refining process, so that the form of inclusions in the steel can be improved, and the impact toughness of the steel is improved, but excessive addition is easy to reduce the cleanliness of the steel and is unfavorable for the low-temperature toughness of the steel; particularly, the Mg treatment adopted in the invention has similar effects, and the formation of calcium aluminate is easily caused by the excessive addition amount of Ca, but the dispersion of the inclusion is not facilitated. The proper addition amount of Ca is less than or equal to 0.0020 percent.

Boron (B): under the combined action of other elements, the hardenability of the steel is obviously improved. For extreme specification pipeline steel, the addition of B is not beneficial to the structural property uniformity of the material. The content of B in the steel should be strictly limited.

The manufacturing method of the 25.4mm hot continuous rolling limit specification pipeline steel plate coil comprises the following steps:

A) smelting and casting: smelting, refining and continuously casting according to components to obtain a plate blank, wherein the thickness of the plate blank is 230 mm;

B) cooling the plate blank: the slab is cooled to below 420 ℃ to completely transform the slab, through the measure, austenite-ferrite phase transformation is completed in the slab cooling process, ferrite-austenite phase transformation occurs in the subsequent slab heating process, and fine initial austenite grains of the slab are ensured to be obtained, if the slab charging temperature is too high, the coarseness and the unevenness of the austenite grains of the slab are easily aggravated, and the DWTT performance of a final coil is not good;

C) heating the plate blank: heating the cooled plate blank, wherein the whole heating furnace gas temperature does not exceed 1200 ℃ in the heating process, the tapping temperature of the plate blank is 1130-1170 ℃, and the temperature is kept for 90-120 min above 1130 ℃, and the crystal grain size is increased along with the increase of the heating temperature or the increase of the heat-preserving time in the heating process of the plate blank, wherein the influence of the crystal grain size is more obvious, and the process is irreversible, so the whole heating furnace gas temperature must be controlled within a proper range; meanwhile, in order to avoid excessive growth of crystal grains in the heat preservation process and ensure uniform temperature of the plate blank, the heat preservation temperature and the heat preservation time of the plate blank are controlled within proper ranges;

D) rough rolling: rolling the plate blank discharged from the furnace in the step C), wherein the rolling pass is 5-6 passes, the final rolling temperature of rough rolling is 930-990 ℃, the thickness of the plate blank after the rough rolling is 58-62 mm, when each pass of the rough rolling enters the rolling mill, starting high-pressure water for descaling, reducing the surface temperature, increasing the deformation resistance gradient in the thickness direction of the plate blank so as to increase the center deformation effect and improve the tissue uniformity in the plate thickness direction, and the rolling speed of the last two passes is 3-4 m/s, and simultaneously reducing the rolling speed as much as possible in the rough rolling process so as to reduce the rolling load and improve the deformation recrystallization effect;

E) finish rolling: finish rolling the plate blank after the rough rolling in the step D) by a 7-frame continuous rolling unit, adopting 5-6 times of finish rolling, wherein the initial rolling temperature is lower than 930 ℃, the final rolling temperature is 780-820 ℃, and by reducing the finish rolling times, the deformation reduction rate of the times can be improved, the deformation effect of the plate thickness center part can be improved, and the uniformity of the structure performance in the plate thickness direction can be improved; meanwhile, the low initial rolling and final rolling temperatures are beneficial to increasing the distortion of austenite grains and creating favorable conditions for uniform nucleation of acicular ferrite in the subsequent cooling process;

F) and (3) controlling cooling: the steel plate is cooled to 250-370 ℃ at a speed of 25-45 ℃/s, then coiled, and cooled at a high speed, so that the steel plate can avoid phase transformation of high-temperature ferrite and pearlite, and meanwhile has a good inhibiting effect on the formation of large-size granular bainite, but when the cooling speed exceeds 45 ℃/s, the uniformity difference of the structure performance in the plate thickness direction is too large, so that the steel plate is unfavorable for cold bending and DWTT performance, and the steel plate adopts a low final cooling temperature, so that the plate thickness center can obtain a high cooling speed in the whole bainite phase transformation area, further the formation of the large-size granular bainite is inhibited, and the steel plate also has an important effect on improving the low-temperature toughness of the material.

Preferably, in the step a), the Mg treatment is performed after the RH vacuum treatment and is added in the form of an Al — Mg alloy wire to improve the effect of the inclusion dispersion treatment.

Preferably, in the step D), the reduction rate of each pass of the last two passes of rough rolling is not less than 23%.

Preferably, in the step E), the 4 th to 5 th frames or the 4 th frame is a dummy frame.

Compared with the prior art, the invention has the following advantages:

1. by adopting the microalloying design of ultralow C-Mn, low Mo-Nb and Ti, combining the dispersion technology of Mg treatment inclusions and various structural refinement and homogenization control process measures, the 25.4mm hot continuous rolling extreme specification pipeline steel plate coil with ultra-fine and homogenized structure is obtained, and has good low-temperature toughness;

2. the microstructure is acicular ferrite and refined granular bainite or quasi-multi-deformation ferrite, the tensile property reaches X65 or X70 steel grade, the mean value of Charpy impact property at minus 20 ℃ is more than or equal to 300J, and the mean value of drop hammer property shearing area at minus 15 ℃ is more than or equal to 85%.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

A25.4 mm hot continuous rolling limit specification pipeline steel plate coil comprises the following chemical components in percentage by mass: c: 0.029-0.051%, and Si: 0.13 to 0.27%, Mn: 1.08-1.63%, P: less than or equal to 0.012 percent, S: less than or equal to 0.0015 percent, Mo: 0.07 to 0.15%, Nb: 0.037-0.059%, Ti: 0.013-0.024%, Al: 0.011-0.037%, Mg: 0.0003-0.0011%, O: 0-0.0015%, N: less than or equal to 0.0045 percent, and the balance of Fe and inevitable impurities.

The chemical components also comprise: at least one of Cu, Ni, Cr, B, V and Ca, wherein the mass percentage of Cu: less than or equal to 0.30 percent, Ni: less than or equal to 0.30 percent, Cr: less than or equal to 0.30 percent, B: less than or equal to 0.0005%, V: less than or equal to 0.030 percent, Ca: less than or equal to 0.0020 percent.

Wherein, when the C content is 0.029-0.045%, the Mn content is 1.42-1.63%, and when the C content is 0.046-0.051%, the Mn content is 1.08-1.41%. To obtain better effect, P: less than or equal to 0.010 percent, S: less than or equal to 0.0010 percent, N: less than or equal to 0.0040 percent.

In addition, the 25.4mm hot continuous rolling limit specification pipeline steel plate coil is characterized in that the structure is acicular ferrite and refined granular bainite or quasi-multi-deformation ferrite, the proportion of the acicular ferrite at the position of 1/4 mm plate thickness is not less than 75%, the proportion of the refined granular bainite or quasi-multi-deformation ferrite is not more than 25%, and the size is not more than 6 μm; the proportion of acicular ferrite at 1/2 position of the plate thickness is not less than 50%, the proportion of refined granular bainite or quasi-multi-deformed ferrite is not more than 50%, and the size is not more than 8 μm.

The invention relates to a method for manufacturing a 25.4mm hot continuous rolling limit specification pipeline steel plate coil, which comprises the following steps:

A) smelting and casting: smelting, refining and continuously casting according to components to obtain a plate blank, wherein the thickness of the plate blank is 230mm, and Mg is added in an Al-Mg alloy wire mode after RH vacuum treatment;

B) cooling the plate blank: cooling the slab to below 420 ℃;

C) heating the plate blank: heating the cooled plate blank, wherein the temperature of heating furnace gas in the heating process is not more than 1200 ℃ in the whole process, the discharging temperature of the plate blank is 1130-1170 ℃, and the temperature is kept above 1130 ℃ for 90-120 min;

D) rough rolling: rolling the plate blank discharged from the furnace in the step C), wherein the rolling pass is 5-6 passes, the 4 th-5 th rack or the 4 th rack is nominal, the final rolling temperature of rough rolling is 930-990 ℃, the thickness of the plate blank after the rough rolling is 58-62 mm, when each pass of rough rolling enters a rolling mill, starting high-pressure water for descaling, the rolling speed of the last two passes is 3-4 m/s, and the pass reduction rate of the last two passes of rough rolling is not lower than 23%;

E) finish rolling: finish rolling the plate blank after the rough rolling in the step D) by a 7-stand continuous rolling unit, wherein the finish rolling is performed for 5-6 times, the initial rolling temperature is lower than 930 ℃, and the final rolling temperature is 780-820 ℃;

F) and (3) controlling cooling: cooling to 250-370 ℃ at a speed of 25-45 ℃/s, and coiling.

X65-grade example 1, X65-grade example 2, X65-grade example 3, X65-grade example 4, X70-grade example 1, X70-grade example 2, X70-grade example 3, X70-grade example 4, and comparative example 1, comparative example 2, comparative example 3, and comparative example 4 are set according to the mass percentage of chemical components. The specific component values are as follows:

TABLE 1 tabulated values of the ingredients (wt,%) for the inventive and comparative examples

The above examples and comparative examples were manufactured according to the process parameters of the following table:

TABLE 2 List of the main process parameters of the examples of the invention and the comparative examples

The examples and comparative examples prepared have the following main properties:

TABLE 3 Main Properties of the inventive and comparative examples

As can be seen from tables 1-3, the thickness of each example of the invention reaches 25.4mm, CVN is more than or equal to 300J at minus 20 ℃, DWTT-SA is more than or equal to 85 percent at minus 15 ℃, and the performance is far better than that of the comparative example.

According to the 25.4mm hot continuous rolling limit specification pipeline steel plate coil and the manufacturing method thereof, the 25.4mm hot continuous rolling limit specification pipeline steel plate coil with ultrafine and homogenized tissues is obtained by adopting the microalloying design of ultralow C-Mn, low Mo-Nb and Ti, combining the Mg treatment impurity dispersion technology and various tissue refining and homogenization control process measures, and has good low-temperature toughness; the microstructure is acicular ferrite and refined granular bainite or quasi-multi-deformation ferrite, the tensile property reaches X65 or X70 steel grade, the mean value of summer impact property at minus 20 ℃ is more than or equal to 300J, and the mean value of drop hammer property at minus 15 ℃ is more than or equal to 85 percent; and the manufacturing method can be widely applied to the hot continuous rolling pipeline steel with the ultra-thick specification of 22-25.4 mm.